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If your friends and family get fat, chances are you
will too, researchers report in a startling new study that suggests
obesity is "socially contagious" and can spread easily from person to
person.
The large, federally funded study found that to be
true even if your loved ones lived far away. Social ties seemed to play
a surprisingly strong role, even more than genes are known to do.
“We were stunned to find that friends who are
hundreds of miles away have just as much impact on a person's weight
status as friends who are right next door,” said co-author James Fowler
of the University of California, San Diego.
The study found a person's chances of becoming
obese went up 57 percent if a friend did, 40 percent if a sibling did
and 37 percent if a spouse did. In the closest friendships, the risk
almost tripled.
Researchers think it's more than just people with
similar eating and exercise habits hanging out together. Instead, it may
be that having relatives and friends who become obese changes one's idea
of what is an acceptable weight.
Despite their findings, the researchers said people
should not sever their relationships.
"There is a ton of research that suggest that having more friends
makes you healthier," Fowler said. "So the last
thing that you want to do is get rid of any of your friends."
The study was published in Thursday's New England
Journal of Medicine and funded by the National Institute on Aging.
Researchers analyzed medical records of people in
the Framingham Heart Study, which has been following the health of
residents of that Boston suburb for more than a half century. They
tracked records for relatives and friends using contact information that
participants provided each time they were examined over a 32-year
period.
In all, 12,067 people (all Framingham participants) were involved in the
study.
After taking into account natural weight gain and
other factors, researchers found the greatest influence occurred among
friends and not in people sharing the same genes or living in the same household. Geography and
smoking cessation had no effect on obesity risk.
On average, the researchers calculated, when an
obese person gained 17 pounds, the corresponding friend put on an extra five
pounds.
Gender also had a strong influence. In same-sex
friendships, a person's obesity risk increased by 71 percent if a friend
gained weight. Between brothers, the risk was up by 44 percent and 67
percent between sisters.
Indiana University statistician Stan Wasserman said while the
study was clever, it had its limitations because it excluded
relationships outside of the Framingham group.
Obesity is a global public health problem. About
1.5 billion adults worldwide are overweight, including more than 400
million who are obese. Two-thirds of Americans are either overweight or
obese.
Much of the recent research focus has been on the
intense hunt for obesity genes involved in appetite or calorie burning.
Treatment has been mainly centered on helping individuals curb their
weight through better diet and fitness.
The findings could open a new avenue for treating
this worldwide epidemic. The researchers said it might be helpful to
treat obese people in groups instead of just the individual.
“Because people are interconnected, their health is
interconnected,” said lead author Dr. Nicholas Christakis, a Harvard sociologist.
Obesity experts not involved in the research said
the results back up what they have suspected all along - that people
look toward one another for what is an acceptable weight.
“If you're just a little bit heavy and everyone
around you is quite heavier, you will feel good when you look in a
mirror,” said Dr. David Katz, director of Yale University's Prevention Research Center.
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